Effect of WC on the microstructure and mechanical properties of TiB2-CoNi cermets

The microstructure and mechanical properties of the vacuum sintered (80-x)TiB2-xWC -10Co-10 Ni (x = 0, 2.5, 5, 7.5, 10, 12.5) cermets were studied by XRD, SEM, EPMA and TEM analysis. The results show that the TiB2-7.5 WC based cermets exhibited excellent comprehensive properties with relative density, Rockwell hardness, transversal rupture strength and fracture toughness of 99.44 +/- 0.18 %, 17.50 +/- 0.71 GPa, 2108 +/- 29 MPa, and 12.21 +/- 0.29 MPa m1/2, respectively. The XRD diffraction peaks of TiB2, W2CoB2, WB and CoNi binder were detected in cermets with WC addition. The HCP TiB2 core -FCC (Ti, W, Co, Ni) (B, C) rim structure was formed in TiB2-WC based cermets with FCC CoNi binder. The coherent interface formed between the TiB2 core and (Ti, W, Co, Ni) (B, C) rim phase, as well as the amorphous CoNi thin layer formed at the interface between (Ti, W, Co, Ni) (B, C) rim and CoNi binder phase, both of them were suggested to improve the interfacial bonding strength of TiB2-WC based cermets.